Receiving circuit



v.lune 24, 1930.

E. T. FLEwELLlNG. JR

m-:csryxgndr CIRCUIT Fiied Slept. 25. 1924 Patented June 24, 1930 EDMUND 'I'. FLEWELLING, JR., OF HGHLAND EAB-K, LLENOIS, ASSGNR TO BUELL y MANUFACTURING co., orcnronsfo, inninors, a

CRPURATION 0F ILLN 01S Application filed September 25, 1924.

This invention relates to radio receiving circuits, and among other objects aims to provide an improved receiving system for either damped or undamped Waves which, Without an external heterodyne, may largely amplify the incoming signal.

The invention may be understood by reterence to the illustrative embodiments shown diagrammatically in the accompanying drawings, in which:

Fig. 1 is a diagram of a system embodying the invention;

Fig. 2 is a diagram of a modified system; and

Fig. 3 is a further modilication.

It is to be understood that the illustrative forms shown in the drawings are simply various embodiments of the invention, and that in the following explanation, the described details of arrangement and organization are merely exemplary.

In the regenerative feed back system employing a grid condenser, it is Well known that under proper adjustment for reception of signals, means must be provided to allow the accumulated charge upon the grid oi" the vacuum tube to leak olii so that it may be free to receive the next incoming signal. It has been observed that by adjustment of a suitable variable high resistance (used as a grid leak), the grid may be freed almost at Will. In such a regenerative receiver, as the grid is blocked by an accumulated charge and freed by leakage of the charge through the grid leak, it will be noticed at some adjustment of the grid leak that one will hear in the telephone receivers a single clicking sound and that this sound by adjustment of the grid leak may be caused to occur oftener or less often than once every second. As this frequency is increased by adjustment of the system it has been found that the rapidity of occurrence of the clicks creates a low musical note increasing in pitch as adjustment is continued until it is so high as'to pass beyond the limits of human hearing.

It' a regenerative receiver is adjusted to the point of oscillation (When amplification is greatest), and the grid is alternately blocked and freed by adjustment of the grid Serial 11o. 739,771.

leak, this action may be properly timed so as not to destroy the incoming signal. For best results, the leakage yfrom the grid should be confined to the grid leak; hence a hard or high vacuum tube should be used,

as Will be understood.

1n Fig. 1 is shoivn diagrammatically a receiving circuit which gives excellent amplification under ythe above conditions. The

circuit includes variable inductances 5, 6,

grid condenser 16 has an adjustable high resistance or grid leak 17 shunted across it, thus permitting freeing of the grid at any desired rate.

In my improved receiving set, shovvn in Fig. 1, a group of three condensers is placed in the circuit, tivo of the condensers 18 and 19 being iXed and connected to the iilament end of the inductance, the third condenser 20 being shunted across the other tvvo and preferably having a shunted variable resistance 21. With the circuit shown, it has been found that, Within certain limits, the larger the capacity of the condensers 18, 19 and 20, the greater the amplification; the condenser capacity Which gives the best results generally being about 0.006 microfarad for each condenser. It Was further found that if condenser 20 is of the correct capacity, it is generally unnecessary to vary both the grid leak and the variable resistance 21, in tuning the circuit. Nor are considerable adjustments in tne grid leak usually necessary for large changes in Wave length. 1

In actual use of the system shown in Fig. 1, any signals received are enormously amplified; in tact, audible signals are receivable with the circuit Without the use of any other antenna or ground than that aii'orded by the Wiring and component parts ofV the receiving system itself. However, the system may, of course, be used with an ordinary grounded antenna; or it will satisfactorily receive signals if used with a loop aerial, with an antenna without a ground, or with a ground without an antenna. EX- cellent reception has been secured by use of an antenna with no ground.

In Fig. 2 there is shown much the same circuit as in Fig. 1, except that the inductances 5a, 6*L are close coupled and are not variable, and the condensers 19 and 2() and the variable resistance 21 are omitted, the condenser 1S, however, being retained. This circuit has not been found to give results as excellent as the circuit of AFig. 1, but it worlrs satisfactorily.

The arrangement in Fig. 3 lis precisely the same as that of Fig. 2, except for the addition of a variable resistance 22 in the shunt 23.

Obviously, the present invention is not restricted to the particular embodiments thereof herein shown and described. Moreover, it is not indispensable that all the features of the invention be used conjointly since they may be employed adi/antageously in various combinations and subcombinations as defined in the claims.

Having described my invention what l claim is:

l. A receiving set comprising a receiving circuit, a grid circuit containing not less than two capacities in series between the grid and filament, and a plate circuit containing two reactances in series between the plate and filament, one of said reactances being the sound producing means and the other constituting an inductive feed-back means, a shunt connection from a point in the plate circuit separated from the plate by one of said reactances and from the filament by the other of said reactances, said shunt connection being branched to tap the grid circuit on opposite sides of one of said grid circuit capacities, a condenser in each branch of said shunt, a variable leak around the shunt condenser connected to the grid circuit remote from the filament, and means for delivering incoming signals to said grid circuit.

2. A receiving set comprising a grid circuit containing not less than two capacities in series between the grid and filament, and a plate circuit containing two reactances in series between the plate and filament, a shunt connection from a point in the plate circuit separated from the plate by one of said reactances and from the filament by the other of said reactances, to a point in the grid circuit separated from the filament by one of said capacities and from the grid by lthe other of said capacities, and means for delivering incoming signals to said grid cir-k cuit.

3. A receiving set comprising a grid circuit containing not less than two capacities in series between the grid and filament, and a plate circuit containing two reactances in series between the plate and filament, one of said reactances being the sound producing means and the other constituting a feed-back means, a shunt connection from a point in the plate circuit separated from the plate by one of said reactances and from the filament by the other of said reactances, to a point in the grid circuit separated from the filament by one of said capacities and from the grid by the other of said capacities, and means for delivering incoming signals to said grid circuit.

il. A receiving set comprising a grid circuit containing not less than two capacities in series between the grid and filament, and a plate circuit containing two reactances'in series between the plate and filament, one of said reactances being the sound producing means and the other constituting an inductive feed-back means, a shunt connection from a point in the plate circuit separated from the plate by one of'said reactances and from the filament by the other of said reactances, said shunt connection being branched to tap the grid circuit on `opposite sides of one of said grid circuit capacities, a condenser in one branch of said shunt, and means for delivering incoming signals to said grid circuit.

5. A receiving set comprising a grid circuit containing not less than two capacities in series between the grid and filament, and a plate circuit containing two inductive reactances in series between the plate and lilament, a shunt connection from a point in the plate circuit separated from the plate by one of said reactances and from the filament by the other of said reactances, said shunt connection being branched to tap the grid circuit on opposite sides of one of said grid circuit capacities, a condenser in each branch of said shunt, and means for delivering incoming signals to said grid circuit.

6. A receiving set comprising a grid circuit containing not less than two capacities in series between the grid and filament, and a plate circuit containing two reactances in series between the plate and filament, a shunt connection from a point in the plate circuit separated from the plate by one of said reactances and from the filament by the other of said reactances, to a point in the grid circuit, and means for delivering incoming signals to said grid circuit.

ln testimony whereof, l have signed my name to this specification.

EDMUND T. FLEVELLING, Jn. 

